The present invention concerns an improved centrifugal expansion roller for sanding machines, particularly floor sanders.
In machines for sanding floors there are known to be centrifugal expansion rollers provided with an endless sand belt.
Such centrifugal expansion rollers consist of a metal core (generally of aluminium) and of an outer elastomeric annular cover (usually of rubber) fixed to the core. A plurality of longitudinal slits are formed on the outer surface of said annular cover, such slits extending along non-radial planes and having a depth such as to leave an uncut elastomer portion towards the core.
While working, during rotation of the roller, the rubber portions between the slits tend--due to centrifugal force--to deform in a radial sense, thereby dragging the sand belt.
In respect of the conventional sand rollers with sand (abrasive) strips fixed by suitable means, the centrifugal rollers have the advantage of being very easy to produce, while the sand belt is easy to mount.
Nevertheless, said rollers also involve some significant drawbacks.
In fact, each slit on the roller surface presses the abrasive onto the floor simultaneously along the whole generating line of said roller, which consequently moves forward slit by slit, leading to an unsatisfactory quality of the sanded surfaces and causing a loud noise.
To try and overcome the above drawbacks, the centrifugal rollers have been produced with slits extending in a helicoidal sense. But this system--when the roller is pressed onto the floor with the force required to do the sanding--produces an axial component, which tends to drive the sand belt out of the roller hence making this solution unacceptable.